The lithium-ion technology is predestined for a broad territory of service applications. Lithium-ion cells, which are also called lithium polymer cells (or lithium-ion polymer cells), especially when they have a laminated aluminum foil packaging, are notable for qualities including high energy densities, specific energies, and an extremely low self-discharge. Lithium-ion cells possess at least one negative electrode (anode) and a positive electrode (cathode), with the ability to perform reversible insertion and removal of lithium ions, this being referred to also as intercalation and deintercalation, respectively. Conductive salt used in lithium-ion cells is mostly lithium hexafluorophosphate (LiPF6).
On account of the high energy densities, both gravimetric and volumetric, of lithium-ion cells, there is particular interest in high intrinsic safety for lithium-ion cells.
For lithium-ion cells, the negative electrode is conventionally divided from the positive electrode by a separator, which is itself an electrical insulator.
Employed very frequently in lithium-ion cells are porous polyolefin separators, which may be polyethylene (PE) or polypropylene (PP) based. In the case of polyolefin separators, however, at temperatures in the region of the softening point of the polymer, the separator may suffer shrinking all around its sides.
Other separators made from high-melting-point polymers, polyimide separators being an example, are indeed more thermally and mechanically stable than polyolefin separators, but in the case of high-capacity cells, of from 40 Ah to 80 Ah, for example, even polyimide separators are not always able to show sufficient intrinsic safety under mechanical or thermal stress.
EP 1 657 767 A1 describes a secondary battery having a porous layer that comprises ceramic particles and a binder and that is applied to at least one of the electrodes of the secondary battery.
DE 10 2009 002 680 A1 describes a ceramic composite material which comprises a polymer film having a regular perforation, the perforation being hidden on at least one side by a porous coating containing ceramic particles.
WO 98/59387 A2 describes an electrochemical cell which comprises calcium carbonate.
WO 00/42672 A2 describes an electrochemical cell which comprises at least one salt of oxalic acid and at least one salt of a carboxylic acid as acid scavengers.
EP 1 146 576 A1 describes a separator for a lithium battery that has a ceramic composite layer and a microporous polymer layer.